The SPCA is appealing to the public for information after a dog was found in Christchurch with multiple rubber bands around his testicles.
The dog was found in Bishopdale Park on Wednesday and it appears to be an attempt at DIY castration.
An SPCA spokesperson said as a result, he had a swollen, bleeding, smelly necrotic mass.
He was taken immediately into surgery, where he was castrated under anaesthetic and was now much better, and expected to make a full recovery, they said.
Not knowing his name, SPCA staff have called the dog "Dave".
SPCA Inspector Sam Cairns said they were not sure how long the dog had had to suffer with the rubber bands tightly bound around his testicles.
"He has distinctive markings and is approximately 9 months old, so someone must know where he came from and who did this to him.
"Dog castration is a straight-forward surgical procedure that must be performed by a veterinarian and under general anaesthetic. Any attempt to perform this kind of surgery 'at home' on a dog is illegal."
Dave would have suffered a great deal of pain for many days or even weeks, he said.
"The pain this sweet boy was in when we found him was immeasurable, so I'm pleased we were able to get him straight into surgery.
"Animals are wholly dependent on their owners to meet their needs, and in this case, this dog did not receive the care it deserved by its owner. A DIY castration is a dreadful way to inflict pain, and the infection alone could have had serious consequences for him."
• Anyone who knows anything about the dog "Dave" or how he came to be in this situation is asked to phone the SPCA Christchurch Centre on 03 349 7057.